It has previously been assumed for MIMO systems that the time dispersion between one or more of the transmit antennas and one or more of the receive antennas was negligible, i.e., the various paths were nonresolvable, as often occurs in low bandwidth systems, because the pulse width is longer than the channel time dispersion. However, it has been recognized that under typical urban (TU) conditions, i.e., the conditions of the so-called “TU” model, that the time dispersion between one or more of the transmit antennas and one or more of the receive antennas is nonnegligible. Such a non negligible time dispersion causes the various paths to interfere with each other, resulting in a bit error rate floor, i.e., minimum, and so the resulting bit error rate is unacceptable.
I. Ghauri and D. Slock have shown, in “Linear Receivers for the DS-CDMA Downlink Exploiting Orthogonality of Spreading Codes”, 32nd Asilomar Conference, Nov. 1-4, 1998 pp. 650-4, that a minimum mean square error (MMSE) equalizer operating on received code division multiple access (CDMA) chips can be employed to compensate for time dispersion in a single transmit, single receive antenna system, thus reducing the bit error rate floor and improving performance.